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Operating Manual - MFA-8000 and MFA-6000 Power Amplifier
Input Ground
The CHASSIS GROUND terminal is internally
connected to the chassis, the AC earth ground, and the
power amplifier’s signal ground. The INPUT GROUND
terminal is tied to the XLR pin 1 and the 1/4" jack sleeve.
It is recommended that the input and chassis ground ter-
minals remain connected with the factory-supplied jumper
strap.
In situations where the power amp and its signal
source are separated by great distances, a ground voltage
difference may exist between the amp’s chassis ground
and the input cable’s ground. Connection of these two
grounds through the jumper strap may cause large ground
currents to flow (which is known as a ground loop), caus-
ing a hum noise in the amp’s output. Unless you have such
a situation with a hum problem that cannot be solved by
using balanced input connections, the ground jumper strap
should remain in place.
7.2 Normal/Bridging Switch
This switch selects between NORMAL mode in
the “out” position where both channels are in-phase, and
BRIDGING mode in the “in” position where channel 1
input is used to drive both channels, inverting the phase
of channel 2. In BRIDGING mode, the channel 1 red bind-
ing post is the (+) in- phase speaker output terminal and
the channel 2 red binding post becomes the (-) out-of-phase
speaker terminal. It is not necessary to depress the MONO
switch in order to operate in BRIDGED mode. The
BRIDGING switch overrides either setting of the Stereo/
Mono Switch.
7.3 Stereo/Parallel Mono Switch
This switch selects between STEREO mode in the
“out” position and PARALLEL MONO mode in the “in”
position. In PARALLEL MONO mode, channel 1 and
channel 2 inputs are internally tied together before the
input attenuator, allowing discrete channel control of a
mono signal. CAUTION: Be sure not to have two signal
sources connected to ch.1 and ch.2 inputs when in paral-
lel mono mode, as it would short-circuit these two signals
and result in no output.
7.4 Level Controls
The level controls allow attenuation (calibrated
in dB) of the input signal. In PARALLEL MONO mode,
channel 1 and channel 2 inputs are tied together, while
still preserving independent level control per channel. In
BRIDGED mode, use only channel 1 level control. It is
recommended that the level controls be operated at full
level (0 dB attenuation) in most situations to maximize
the headroom in the signal source.
7.5 Speaker Outputs - Binding Posts
Caution: This product can deliver enough
energy to the output terminals to produce a lethal
shock. Do not attempt to wire the amplifier when
the power is turned on.
A pair of dual banana binding posts provide the
stereo speaker outputs. In BRIDGING mode, the channel
1 red binding post is the (+) in-phase speaker output ter-
minal and the channel 2 red binding post becomes the (-)
out-of-phase speaker terminal.
CAUTION! NEVER CONNECT THE
TWO RED BINDING POSTS TOGETHER OR
CONNECT EITHER RED BINDING POST TO
A BLACK BINDING POST!
o
no Mode:
dged
n
2+ is neg
n
1+ is pos
CHANNEL 2
OUTPUT
CHANNEL 1
OUTPUT
1+ is POS
1- is GND
1+ is POS
1- is GND
a
l Channel
n
nector
a
n.1
n
1+, Pin1-
a
n.2
n
2+, Pin2-
(-)
(+)
(+)
(-)
BRIDGE
(+)
(-)
1
5
MDA 20A
Channel 2
Ashl
y
Ma
d
M
F
750
W
1200
W
Figure 7.5: Output Section